READING: Chapter 9 sections 1 – 3 HOMEWORK – DUE TUESDAY 11/10/15

HW-BW 9.1 (Bookwork) CH 9 #'s 5, 6, 10, 51, 53, 54, 57 – 67 (odd), 86, 88, 89

HW-WS 16 (Worksheet) (from course website) HOMEWORK – DUE THURSDAY 11/12/15

HW-BW 9.2 (Bookwork) CH 9 #’s 27, 28, 29, 31, 33, 37, 38, 40, 47, 48, 49 HW-WS 17 (Worksheet) (from course website)

Lab Wednesday/Thursday – EXP 12

No prelab

Next Monday/Tuesday – EXP 13 Prelab

Types of Bonding : Ionic Compounds

Ionic bonding involves the complete TRANSFER of electrons from one atom to another.

Usually observed when a metal bonds to a nonmetal.

++ + +

+ + + ++ + +

- -

-

-- -

-

-

-

-

+ + ++ + ++ + +

- -

-

- -

-

-

-

-

-

Types of Bonding : Ionic Compounds

Ionic bonding involves the complete TRANSFER of electrons from one atom to another.

Usually observed when a metal bonds to a nonmetal.

Metals have low ionization energy, making it relatively easy to remove electrons from them

Nonmetals have high electron affinities, making it advantageous to add electrons to these atoms

The oppositely charged ions are then attracted to each other, resulting in an ionic bond

Ionic compounds tend to be hard, rigid, and brittle, with high melting points.

Types of Bonding: Ionic Compounds

Ionic compounds tend to be hard, rigid, and brittle, with high melting points.

Ionic compounds do not conduct electricity in the solid state. In the solid state, the ions are fixed in place in the lattice and do not

move.

Types of Bonding: Ionic Compounds

Ionic compounds tend to be hard, rigid, and brittle, with high melting points.

Ionic compounds do not conduct electricity in the solid state. In the solid state, the ions are fixed in place in the lattice and do not

move. Ionic compounds conduct electricity when melted or dissolved.

In the liquid state or in solution, the ions are free to move and carry a current.

Types of Bonding: Ionic Compounds

Covalent bonding involves the SHARING of electrons

Usually observed when a nonmetal bonds to a nonmetal.

Types of Bonding: Covalent Compounds

+

+ +

+

6p+

-

-

-

-

-

-

-

-

-

-

Covalent bonding involves the SHARING of electrons

Usually observed when a nonmetal bonds to a nonmetal.

Nonmetal atoms have relatively high ionization energies, so it is difficult to remove electrons from them

When nonmetals bond together, it is better in terms of potential energy for the atoms to share valence electrons

Potential energy lowest when the electrons are between the nuclei, holding the atoms together by attracting nuclei of both atoms

Types of Bonding: Covalent Compounds

Metallic bonding involves electron POOLING

Occurs when a metal bonds to another metal.

Types of Bonding: Metals

The relatively low ionization energy of metals allows them to lose electrons easily

Metallic bonding involves the metal atoms releasing their valence electrons to be shared as a pool by all the atoms/ions in the metal

Organized metal cations islands in a sea of electrons

Electrons delocalized throughout the metal structure

Bonding results from attraction of cation for the delocalized electrons

Explains many of the properties of metals

Types of Bonding: Metals

Lewis Dot Symbols: Elements and Ions

Lewis dot structures of elementsUse the symbol of element to represent nucleus and inner

electronsUse a dot to represent each valence electron in the atom

Na Ca In

N O F H

Sn

Xe

Atoms bond because it results in a more stable electron configuration. more stable = lower potential energy

Atoms bond together by either transferring or sharing electrons

Usually this results in all atoms obtaining an outer shell with eight electrons octet rule there are some exceptions to this “rule”!!

Lewis Dot Symbols: Octet Rule

When atoms bond, they tend to gain, lose, or share electrons to result in eight valence electrons

noble gas configuration - ns2np6

Many exceptionsH, Li, Be, B attain an electron configuration like He

Helium = two valence electrons, a duet Lithium loses its one valence electron Hydrogen shares or gains one electron

o commonly loses its one electron to become H+ Beryllium loses two electrons to become Be2+

o commonly shares its 2 electrons in covalent bonds, resulting in 4 valence electrons Boron loses three electrons to become B3+

o commonly shares its 3 electrons in covalent bonds, resulting in 6 valence electronsexpanded octets for elements in Period 3 or below

using empty valence d orbitalsBasically, only C, N, O, F, and Ne MSUT follow the octet rule

Lewis Dot Symbols: Octet Rule

Cations have Lewis symbols without valence electronslost in the cation formation

Anions have Lewis symbols with eight valence electronselectrons gained in the formation of the anion

Lewis Dot Symbols: Elements and Ions

Li Li+ F [ ]F–1

Orbital diagrams

Lewis electron-dot symbols

Electron configurations Li 1s22s1 + F 1s22s22p5

Li ↑↓

1s 2p

↑

2s

↑↓↑↓

1s 2p

↑↓

2s

↑↓ ↑F

+

↑↓

1s 2p2s

Li+

↑↓

1s 2p

↑↓

2s

↑↓ ↑↓ ↑↓F-

Li• F••

••••• Li+ + F

••

••••••

–

Lewis Dot Symbols and Other Electron Stuff

→ Li+ 1s2 + F– 1s22s22p6

Covalent bonding involves the SHARING of electrons

Usually observed when a nonmetal bonds to a nonmetal.

Nonmetal atoms have relatively high ionization energies, so it is difficult to remove electrons from them

When nonmetals bond together, it is better in terms of potential energy for the atoms to share valence electrons

Potential energy lowest when the electrons are between the nuclei, holding the atoms together by attracting nuclei of both atoms

Types of Bonding: Covalent Compounds

Covalent Bonds

Covalent BondsAtoms share electrons to achieve a full outer level of electrons. The shared electrons are called a shared pair or bonding pair.

H

••

H or H–H

The shared pair is represented as a pair of dots or a line:

An outer-level electron pair that is not involved in bonding is called a lone pair, nonbonding pair, or unshared pair.

••F••

••••

F••

••

••

••

••F–F

•• ••

or••

••

Covalent Bonds

The bond order is the number of electron pairs being shared by a given pair of atoms.

A single bond consists of one bonding pair and has a bond order of 1A double bond consists of two bonding pair and has a bond order of

2A triple bond consists of three bonding pair and has a bond order of 3

The bond energy (BE) is the energy needed to overcome the attraction between the nuclei and the shared electrons. The stronger the bond the higher the bond energy.

The bond length is the distance between the nuclei of the bonded atoms.

For a given pair of atoms, a higher bond order results in a shorter bond length and higher bond energy.

Between any two atoms, more bonds = shorter bondsBetween any two atoms, more bonds = larger bond energy

Covalent Bonds

For a given pair of atoms, a higher bond order results in a shorter bond length and higher bond energy.

Between any two atoms, more bonds = shorter bondsBetween any two atoms, more bonds = larger bond energy

Bond length increases down a group in the periodic table and decreases across the period.

Bond energy shows the opposite trend.

Covalent Bonds

Internuclear distance(bond length)

Covalent radius

133 pm

Internuclear distance(bond length)

Covalent radius

72 pm

Covalent Bonds: DHrxn

The heat released or absorbed during a chemical change is due to differences between the bond energies of reactants and products.

DHºrxn = SDHºreactant bonds broken - SDHºproduct bonds formedDHºrxn = SDHºreactant bonds broken - SDHºproduct bonds formedDHºrxn = SDHºreactant bonds broken - SDHºproduct bonds formed

reactants products

always + always -

Bond breaking is endothermic, DH(breaking) = +Bond making is exothermic, DH(making) = −

Covalent Bonds: DHrxn

4(C–H bond = 413 kJ)

O=O bond = 498 kJ

C–H bond = 413 kJ

DHºrxn = SDHºreactant bonds broken - SDHºproduct bonds formed

2(O=O bond = 498 kJ)2(O=O bond = 498 kJ) = 996 kJ

4(C–H bond = 413 kJ) = 1652 kJ 2(C=O bond = 799 kJ)C=O bond = 799 kJ2(C=O bond = 799 kJ) = 1598 kJ

O–H bond = 467 kJ4(O–H bond = 467 kJ)4(O–H bond = 467 kJ) = 1868 kJ

DHºrxn = (1652 kJ + 996 kJ) - (1598 kJ + 1868 kJ)

DHºrxn = - 818 kJ

Electronegativity and Polarity

A covalent bond in which the shared electron pair is not shared equally, but remains closer to one atom than the other, is a polar covalent bond.

X YIf “X” and “Y” share bonding e- equally:

If “X” and “Y” do NOT share bonding e- equally:

X Y X YUnequal sharing of bonding e- leads to polar covalent bonds

Electronegativity and Polarity

A covalent bond in which the shared electron pair is not shared equally, but remains closer to one atom than the other, is a polar covalent bond.

The ability of an atom in a covalent bond to attract the BONDING electrons towards itself is called its electronegativity.

Electronegativity and Polarity

A covalent bond in which the shared electron pair is not shared equally, but remains closer to one atom than the other, is a polar covalent bond.

Unequal sharing of electrons causes the more electronegative atom of the bond to be partially negative and the less electronegative atom to be partially positive.

The ability of an atom in a covalent bond to attract the BONDING electrons towards itself is called its electronegativity.

If EN difference is:EN < 0.5 the bond is considered to be pure covalent

C C C S I HBr Br

2.5-2.5=0 2.5-2.5=0 2.8-2.8=0 2.5-2.1=0.4

2.0 > EN ≥ 0.5 the bond is considered to be polar covalent

3.5-2.5=1 4.0-2.1=1.9 3.0-2.5=0.5 3.5-1.8=1.7

C O Si OF H N C

EN ≥ 2.0 the bond is considered to be ionic

Al :F Ca :O Na :Cl Rb :N1.5-4.0=2.5 1.0-3.5=2.5 0.9-3.0=2.1 0.8-3.0=2.2

Electronegativity and Polarity

The lowercase Greek letter delta, d, is used to indicate a polar bond.

The MORE EN element has extra e-, so it is negative and is indicated by the symbol d–.

The LESS EN element is short of e-, so it is positive and is indicated by the symbol d+.

H – Cl d+ d–

3.02.1

Electronegativity and Polarity

Give delta notation and polarity arrows for the following:

C O Si OF H N Cd+ d– d+d– d+d– d+ d–

2.5 3.5 4.0 2.1 3.0 2.5 1.8 3.5

Electronegativity and Polarity

Lewis Structures

1) Determine the total number of valence electrons available in the chemical

If ion, add 1 electron for each negative charge and subtract 1 electron for each positive

2) Draw the skeletal structure of the molecule using single bonds to connect the atoms

Central atom(s) will be surrounded by other atomsCentral atom(s) tend to be the element that is the least electronegativeH and F always exterior atoms

3) Fill the octets for all atoms except hydrogen (2), beryllium (4) and, boron (6)

Count total electrons drawn and subtract this from the number of valence electrons available found in step #1.

If you have not drawn enough electrons, add the missing ones to the central atom

If you have drawn too many electrons, remove lone pair(s) and add multiple bonds

# of valence e- needed = # of bonds formed (guideline only)